Here's the latest in the all green home: 85 percent recycled Styrofoam walls.

California's building codes are among the toughest in the nation when it comes to energy efficiency, and they will only get tougher
over the next eight years
. New houses in the future may be able to get ahead of the game using sturdy insulation, and homebuilders looking to take their greenness up a notch could consider
Perform Wall
, an insulating panel made mostly from old Styrofoam.

"We liked Perform Wall because it's an environmentally responsible product," said Mary Krebill, who is building her dream house in Elfin Forest, near Escondido. "It resists fire and mold and it's highly insulative. It's a very green product."

Perform Wall is a mix of cement and polystyrene, the generic term for Styrofoam, manufactured in Arizona by El Paso-based
Trilogy Materials Ltd.

"The big electronics companies ship components in foam to be assembled in Mexico," said Wade Vernon, a local distributor. "They (Trilogy) capture that foam from the maquiladoras. It's basically packaging from the home electronics industry."

Vernon said the company doesn't take polystyrene from homes because of the risk of food getting into the mix, and attracting bacteria later.

The raw Perform Wall material costs $4 to $4.50 a square foot, Vernon said. Add in labor and reinforcing rebar, and a Perform Wall costs between $14 and $18 for each square foot of wall.

Pat Lawrence, Mary Krebill's contractor and the man who inspired her to use Perform Wall, said the house would need 8,500 square feet of Perform Wall walls, at a rough average cost of $16 a square foot, which comes to $136,000.

For Krebill, Perform Wall will be part of a suite of green features: solar panels, grey water recapture, and all energy efficient appliances. Even though the home will be more than 5,000 square feet, Krebill expects to far exceed California's strict energy efficiency requirements for new construction.

"Because of the Perform Wall we won't have to use a lot of power," she said. "We won't have to use our heat or HVAC at all."